By Amelia Clive, SMART Trial co-ordinator and respiratory registrar,
North Bristol NHS Trust
Investigators have now published the results of the SMART Trial that investigated the effects of radiotherapy to intervention sites in mesothelioma.
As a complication of interventions to the chest to manage and diagnose mesothelioma, the tumour can spread along the scar tissue, resulting in a chest wall lump (also known as a ‘procedure tract metastasis’ (PTM)) which can be painful and unsightly. Three previous small studies have evaluated whether radiotherapy delivered shortly after chest wall interventions (‘prophylactic radiotherapy’) could prevent this complication from occurring but the results of these trials were conflicting, which has resulted in variation in clinical advice and practice around the world.
The SMART trial was designed to compare giving prophylactic radiotherapy to sites of large chest wall interventions in patients with mesothelioma, with deferred radiotherapy (given only if a PTM developed). 203 patients with proven mesothelioma who had undergone a large bore pleural intervention in the preceding 35 days were recruited from 22 UK hospitals between December 2011 and August 2014. They were randomly allocated to receive either prophylactic radiotherapy (within 42 days of the pleural intervention) or deferred radiotherapy (no radiotherapy initially, but radiotherapy given should a PTM develop). The patients were followed up for 12 months.
We were primarily interested to see if the incidence of PTM differed between the two groups, but we also compared thechest pain, painkiller use, survival and quality of life of the 2 groups and the safety profile of radiotherapy.
The results showed the overall incidence of PTM was low and did not significantly differ between the two groups (9 of 102 (9%) in the prophylactic radiotherapy group developed a PTM, compared with 16 of 101 (16%) in the deferred radiotherapy group). Only 8 of the 25 PTMs identified were tender and the incidence of a tender PTM was also not significantly different in the 2 groups.
Importantly, there was no difference between the groups in terms of their chest pain, painkiller requirements, survival or their quality of life. The radiotherapy was well tolerated with only a small number of patients experiencing mild skin irritation, tiredness and lethargy after it. An economic analysis of prophylactic radiotherapy showed it was not a cost-effective treatment compared with deferred radiotherapy.
Evaluating certain subgroups of patients did reveal some potentially interesting findings. There was some suggestion that prophylactic radiotherapy may be more effective in preventing PTMs in patients who do not go on to have chemotherapy, those with only epithelioid type cells on their biopsy and when the prophylactic radiotherapy was delivered exactly according to the trial protocol. However the number of patients in these groups were too small to draw firm conclusions.
The PIT study, another randomised trial looking at a similar research question which is currently in follow-up may help to clarify further whether certain subgroups of patients may benefit more from prophylactic radiotherapy than others.
Based on the results of the SMART trial, we feel routine use of prophylactic radiotherapy in all patients with mesothelioma who undergo large bore pleural interventions is not justified. However, we would advise careful, active surveillance of patients and prompt treatment of PTMs should they develop as this strategy appears to be equally as effective.
If you would like to discuss results of the SMART trial please call the Mesothelioma UK freephone helpline on 0800 169 2409 or email firstname.lastname@example.org